Amine-aldehyde condensation products are widely employed as chemical activators for effecting free radical-initiated polymerization, notably in compositions such as the acrylate adhesives that are disclosed in Bachmann U.S. Pat. Nos. 4,348,503, 4,429,088, and 4,432,829, and Bachmann et al U.S. Pat. Nos. 4,963,220, 4,964,938, and 5,039,715. Such activators are commercially available from several sources, and are typically used as solutions in 1,1,1-trichloroethylene or alcohol; illustrative products include VANAX 808 (aniline/butyraldehyde) and VANAX 833 (butylamine/butyraldehyde), both sold by R. T. Vanderbilt, Inc., and HEPTEEN BASE (aniline/heptaldehyde), sold by Uniroyal Chemical Corporation.
The inclusion of an inert solvent in an otherwise solvent-free system is of course disadvantageous from a number of standpoints. Such solvents may give rise to flammability, toxicity, and ozone-depletion problems; bond strengths may be reduced due to solvent residues and/or excessive plasticization; shrinkage upon curing may be increased; and evaporation requirements will diminish the convenience, and indeed feasibility, of use for many applications. Needless to say, such disadvantages are encountered irrespective of the particular activator and polymerization formulations involved.